Answer
Please see the work below.
Work Step by Step
We know that
$a=\frac{v^2}{2d}$
We plug in the known values to obtain:
$a=\frac{(42)^2}{(2)(0.05)}=17640\frac{m}{s^2}$
As $F=ma$
$F=(0.145)(17640)=2558N$
Now we can find the torque as
$\tau=rF$
We plug in the known values to obtain:
$\tau=(0.63)(2558)=1600N.m$
